Method for edge sealing barrier films

ABSTRACT

An edge-sealed, encapsulated environmentally sensitive device. The device includes an environmentally sensitive device, and at least one edge-sealed barrier stack. The edge-sealed barrier stack includes a decoupling layer and at least two barrier layers. The environmentally sensitive device is sealed between an edge-sealed barrier stack and either a substrate or another edge-sealed barrier stack. A method of making the edge-sealed, encapsulated environmentally sensitive device is also disclosed.

CROSS REFERENCE OF RELATED APPLICATIONS

This application is a division of application Ser. No. 11/693,022, filedMar. 29, 2007, entitled Method for Edge Sealing Barrier Films, which isa continuation of application Ser. No. 11/112,860, filed Apr. 22, 2005,entitled Method for Edge Sealing Barrier Films, now U.S. Pat. No.7,198,832, which is continuation-in-part of application Ser. No.11/068,356, filed Feb. 28, 2005, entitled Method for Edge SealingBarrier Films, which is a division of application Ser. No. 09/966,163,filed Sep. 28, 2001, entitled Method for Edge Sealing Barrier Films, nowU.S. Pat. No. 6,866,901, which is a continuation-in-part of applicationSer. No. 09/427,138, filed Oct. 25, 1999, entitled Environmental BarrierMaterial for Organic Light Emitting Device and Method of Making, nowU.S. Pat. No. 6,522,067.

This application is related to U.S. patent application Ser. No.10/889,640, filed Jul. 12, 2004 entitled “MULTILAYER PLASTIC SUBSTRATES”now RE40787, issued Jun. 23, 2009; and Ser. No. 10/890,437, filed Jul.12, 2004 entitled “ULTRABARRIER SUBSTRATES” now RE40531, issued Oct. 7,2008.

This application is related to commonly assigned U.S. patent applicationSer. No. 11/693,020, filed Mar. 29, 2007 entitled METHOD FOR EDGESEALING BARRIER FILMS; Ser. No. 10/412,133, filed Apr. 11, 2003 entitled“APPARATUS FOR DEPOSITING A MULTILAYER COATING ON DISCRETE SHEETS”; Ser.No. 11/112,880, filed Apr. 22, 2005 entitled “APPARATUS FOR DEPOSITING AMULTILAYER COATING ON DISCRETE SHEETS”; Ser. No. 11/439,474, filed May23, 2006 entitled “METHOD OF MAKING AN ENCAPSULATED PLASMA SENSITIVEDEVICE” now U.S. Pat. No. 7,510,913, issued Mar. 31, 2009; Ser. No.11/509,837, filed Aug. 24, 2006 entitled “ENCAPSULATED DEVICES ANDMETHOD OF MAKING”; Ser. No. 11/627,583, filed Jan. 26, 2007 entitled“THREE DIMENSIONAL MULTILAYER BARRIER AND METHOD OF MAKING” nowabandoned; Ser. No. 11/627,602, filed Jan. 26, 2007 entitled METHOD OFENCAPSULATING AN ENVIRONMENTALLY SENSITIVE DEVICE; Ser. No. 11/776,616,filed Jul. 12, 2007 entitled “MULTILAYER BARRIER STACKS AND METHODS OFMAKING MULTILAYER BARRIER STACKS” now U.S. Pat. No. 7,648,925; Ser. No.12/345,787, filed Dec. 30, 2008 entitled “METHOD FOR EDGE SEALINGBARRIER FILMS”; Ser. No. 12/341,251, filed Dec. 22, 2008 entitled“ENCAPSULATED WHITE OLEDS HAVING ENHANCED OPTICAL OUTPUT”; Ser. No.12/345,912, filed Dec. 30, 2008 entitled “METHOD FOR EDGE SEALINGBARRIER FILMS”; Ser. No. 12/341,134, filed Dec. 22, 2008 entitledENCAPSULATED RGB OLEDS HAVING ENHANCED OPTICAL OUTPUT and Ser. No.12/345,717, filed Dec. 30, 2008 entitled “METHOD FOR ENCAPSULATINGENVIRONMENTALLY SENSITIVE DEVICES”.

BACKGROUND OF THE INVENTION

The invention relates generally to multilayer, thin film barriercomposites, and more particularly, to multilayer, thin film barriercomposites having the edges sealed against lateral moisture and gasdiffusion.

Multilayer, thin film barrier composites having alternating layers ofbarrier material and polymer material are known. These composites aretypically formed by depositing alternating layers of barrier materialand polymer material, such as by vapor deposition. If the polymer layersare deposited over the entire surface of the substrate, then the edgesof the polymer layers are exposed to oxygen, moisture, and othercontaminants. This potentially allows the moisture, oxygen, or othercontaminants to diffuse laterally into an encapsulated environmentallysensitive device from the edge of the composite, as shown in FIG. 1. Themultilayer, thin film barrier composite 100 includes a substrate 105 andalternating layers of decoupling material 110 and barrier material 115.The scale of FIG. 1 is greatly expanded in the vertical direction. Thearea of the substrate 105 will typically vary from a few squarecentimeters to several square meters. The barrier layers 115 aretypically a few hundred Angstroms thick, while the decoupling layers 110are generally less than ten microns thick. The lateral diffusion rate ofmoisture and oxygen is finite, and this will eventually compromise theencapsulation. One way to reduce the problem of edge diffusion is toprovide long edge diffusion paths. However, this decreases the area ofthe substrate which is usable for active environmentally sensitivedevices. In addition, it only lessens the problem, but does noteliminate it.

A similar edge diffusion problem will arise when a substrate containinga multilayer, thin film barrier composite is scribed and separated tocreate individual components.

SUMMARY OF THE INVENTION

Thus, there is a need for an edge-sealed barrier film composite, and fora method of making such a composite.

The present invention solves this need by providing an edge-sealed,encapsulated environmentally sensitive device. The edge-sealed,environmentally sensitive device includes at least one initial barrierstack comprising at least one decoupling layer and at least one barrierlayer. A first decoupling layer of a first initial barrier stack has anarea and a first barrier layer of the first initial barrier stack has anarea, the area of the first barrier layer of the first initial barrierstack being greater than the area of the first decoupling layer of thefirst initial barrier stack. The first barrier layer of the firstinitial barrier stack is in contact with a third barrier layer or anoptional substrate, sealing the first decoupling layer of the firstinitial barrier stack between the first barrier layer of the firstinitial barrier stack and the third barrier layer or the optionalsubstrate. An environmentally sensitive device is adjacent to the atleast one initial barrier stack. At least one additional barrier stackis adjacent to the environmentally sensitive device on a side oppositethe at least one initial barrier stack. The at least one additionalbarrier stack comprises at least one decoupling layer and at least onebarrier layer. A first decoupling layer of a first additional barrierstack has an area and a first barrier layer of the first additionalbarrier stack has an area, the area of the first barrier layer of thefirst additional barrier stack being greater than the area of the firstdecoupling layer of the first additional barrier stack. The firstbarrier layer of the first additional barrier stack is in contact with afourth barrier layer, sealing the first decoupling layer of the firstadditional barrier stack between the first barrier layer of the firstadditional barrier stack and the fourth barrier layer. At least onebarrier layer of at least one initial barrier stack is in contact withat least one barrier layer of at least one additional barrier stack,sealing the environmentally sensitive device between the at least oneinitial barrier stack and the at least one additional barrier stackforming an environmentally sensitive device seal, wherein an oxygentransmission rate through the environmentally sensitive device seal isless than 0.005 cc/m²/day at 23° C. and 0% relative humidity.

By adjacent, we mean next to, but not necessarily directly next to.There can be additional layers intervening between the substrate and thebarrier stacks, and between the barrier stacks and the environmentallysensitive device, etc.

Another aspect of the invention is a method of making an edge-sealed,encapsulated environmentally sensitive device. The method includesproviding at least one initial barrier stack, the at least one initialbarrier stack comprising at least one decoupling layer and at least onebarrier layer, wherein a first decoupling layer of a first initialbarrier stack has an area and wherein a first barrier layer of the firstinitial barrier stack has an area, the area of the first barrier layerof the first initial barrier stack being greater than the area of thefirst decoupling layer of the first initial barrier stack, and whereinthe first barrier layer of the first initial barrier stack is in contactwith a third barrier layer or an optional substrate, sealing the firstdecoupling layer of the first initial barrier stack between the firstbarrier layer of the first initial barrier stack and the third barrierlayer or the optional substrate; placing an environmentally sensitivedevice adjacent to the at least one initial barrier stack; and placingat least one additional barrier stack adjacent to the environmentallysensitive device on a side opposite the at least one initial barrierstack, the at least one additional barrier stack comprising at least onedecoupling layer and at least one barrier layer, wherein a firstdecoupling layer of a first additional barrier stack has an area andwherein a first barrier layer of the first additional barrier stack hasan area, the area of the first barrier layer of the first additionalbarrier stack being greater than the area of the first decoupling layerof the first additional barrier stack, wherein the first barrier layerof the first additional barrier stack is in contact with a fourthbarrier layer, sealing the first decoupling layer of the firstadditional barrier stack between the first barrier layer of the firstadditional barrier stack and the fourth barrier layer, and wherein atleast one barrier layer of at least one initial barrier stack is incontact with at least one barrier layer of at least one additionalbarrier stack, sealing the environmentally sensitive device between theat least one initial barrier stack and the at least one additionalbarrier stack forming an environmentally sensitive device seal, whereinan oxygen transmission rate through the environmentally sensitive deviceseal is less than 0.005 cc/m²/day at 23° C. and 0% relative humidity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a barrier composite of the prior art.

FIG. 2 is a cross-section of one embodiment of an edge-sealed,encapsulated environmentally sensitive device of the present invention.

FIG. 3 shows a successful barrier layer without a seal after 750 hoursat 60° C. and 90% relative humidity.

FIG. 4 shows a successful edge seal after 750 hours at 60° C. and 90%relative humidity.

FIG. 5 shows a failed edge seal after 750 hours at 60° C. and 90%relative humidity.

FIG. 6 shows a cross-section of one embodiment of a substrate and maskarrangement and a plan view of the resulting seal.

FIG. 7 shows a cross-section of another embodiment of a substrate andmask arrangement and a plan view of the resulting seal.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 shows an edge-sealed, encapsulated environmentally sensitivedevice 400. There is a substrate 405 which can be removed after thedevice is made, if desired. The environmentally sensitive device 430 isencapsulated between initial barrier stack 422 on one side andadditional barrier stack 440 on the other side. There is another initialbarrier stack 420 between the substrate 405 and initial barrier stack422.

The environmentally sensitive device can be any device requiringprotection from moisture, gas, or other contaminants. Environmentallysensitive devices include, but are not limited to, organic lightemitting devices, liquid crystal displays, displays usingelectrophoretic inks, light emitting diodes, light emitting polymers,electroluminescent devices, phosphorescent devices, organic solar cells,inorganic solar cells, thin film batteries, and thin film devices withvias, and combinations thereof.

The substrate, which is optional, can be any suitable substrate, and canbe either rigid or flexible. Suitable substrates include, but are notlimited to: polymers, for example, polyethylene terephthalate (PET),polyethylene naphthalate (PEN), or high temperature polymers, such aspolyether sulfone (PES), polyimides, or Transphan™ (a high glasstransition temperature cyclic olefin polymer available from Lofo HighTech Film, GMBH of Weil am Rhein, Germany); metals and metal foils;paper; fabric; glass, including thin, flexible, glass sheet (forexample, flexible glass sheet available from Corning Inc. under theglass code 0211. This particular thin, flexible glass sheet has athickness of less than 0.6 mm and will bend at a radium of about 8inches.); ceramics; semiconductors; silicon; and combinations thereof.

Barrier stack 420 has a barrier layer 415 which has an area greater thanthe area of the decoupling layer 410 which seals the decoupling layer410 within the area of the barrier layer 415. Barrier stack 422 has twobarrier layers 415, 417 and two decoupling layers 410, 412. Barrierlayer 415 has an area greater than that of the decoupling layers 410,412 which seals the decoupling layers 410, 412 within the area of thebarrier layer 415. There is a second barrier layer 417. Because thedecoupling layers 410, 412 are sealed within the area covered by thebarrier layer 415, ambient moisture, oxygen, and other contaminantscannot diffuse through the decoupling layers to the environmentallysensitive device.

On the other side of the environmentally sensitive device 430, there isan additional barrier stack 440. Barrier stack 440 includes twodecoupling layers 410 and two barrier layers 415 which may be ofapproximately the same size. Barrier stack 440 also includes barrierlayer 435 which has an area greater than the area of the decouplinglayers 410 which seals the decoupling layers 410 within the area ofbarrier layer 435.

It is not required that all of the barrier layers have an area greaterthan all of the decoupling layers, but at least one of the barrierlayers must have an area greater than at least one of the decouplinglayers. If not all of the barrier layers have an area greater than ofthe decoupling layers, the barrier layers which do have an area greaterthan the decoupling layers should form a seal around those which do notso that there are no exposed decoupling layers within the barriercomposite, although, clearly it is a matter of degree. The fewer theedge areas of decoupling layers exposed, the less the edge diffusion. Ifsome diffusion is acceptable, then a complete barrier is not required.

The barrier stacks of the present invention on polymeric substrates,such as PET, have measured oxygen transmission rate (OTR) and watervapor transmission rate (WVTR) values well below the detection limits ofcurrent industrial instrumentation used for permeation measurements(Mocon OxTran 2/20L and Permatran). Table 1 shows the OTR and WVTRvalues (measured according to ASTM F 1927-98 and ASTM F 1249-90,respectively) measured at Mocon (Minneapolis, Minn.) for several barrierstacks on 7 mil PET, along with reported values for other materials.

TABLE 1 Oxygen Water Vapor Permeation Rate Permeation (cc/m²/day)(g/m²/day)⁺ Sample 23° C. 38° C. 23° C. 38° C. Native 7 mil PET 7.62 — —— 1-barrier stack <0.005 <0.005* — 0.46⁺ 1-barrier stack with ITO <0.005<0.005* — 0.011⁺ 2-barrier stacks <0.005 <0.005* — <0.005⁺ 2-barrierstacks with ITO <0.005 <0.005* — <0.005⁺ 5-barrier stacks <0.005 <0.005*— <0.005⁺ 5-barrier stacks with ITO <0.005 <0.005* — <0.005⁺ DuPontfilm¹ 0.3 — — — (PET/Si₃N₄ or PEN/Si₃N₄) Polaroid³ <1.0 — — — PET/Al²0.6 — 0.17 — PET/silicon oxide² 0.7-1.5 — 0.15-0.9 — Teijin LCD film <2— <5 — (HA grade-TN/STN)³ *38° C., 90% RH, 100% O₂ ⁺38° C., 100% RH ¹P.F. Carcia, 46^(th) International Symposium of the American VacuumSociety, October 1999 ²Langowski, H. C., 39^(th) Annual TechnicalConference Proceedings, SVC, pp. 398-401 (1996) ³Technical Data Sheet

As the data in Table 1 shows, the barrier stacks of the presentinvention provide oxygen and water vapor permeation rates several ordersof magnitude better than PET coated with aluminum, silicon oxide, oraluminum oxide. Typical oxygen permeation rates for other barriercoatings range from about 1 to about 0.1 cc/m²/day. The oxygentransmission rate for the barrier stacks of the present invention isless than 0.005 cc/m²/day at 23° C. and 0% relative humidity, and at 38°C. and 90% relative humidity. The water vapor transmission rate is lessthan 0.005 g/m²/day at 38° C. and 100% relative humidity. The actualtransmission rates are lower, but cannot be measured with existingequipment.

In theory, a good edge seal should be no more permeable than the overallbarrier layer. This should result in failure at the edges occurring at arate statistically the same as that observed anywhere else. In practice,the areas closest to the edge show failure first, and the inference isthat edge failure is involved.

The Mocon test for the barrier layers requires significant surface area,and cannot be used to test the edge seal directly. A test using a layerof calcium was developed to measure barrier properties. The calcium testis described in Nisato et al., “Thin Film Encapsulation for OLEDs:Evaluation of Multi-layer Barriers using the Ca Test,” SID 03 Digest,2003, p. 550-553, which is incorporated herein by reference. The calciumtest can be used to evaluate edge seal performance for both oxygentransmission rate and water vapor transmission rate. An encapsulateddevice is made, and the edges are observed for degradation in responseto permeation by oxygen and water. The determination is qualitative:pass/fail. Failure is noted at the edges, and the failure progressesinwards from the edges over time. An edge seal which passes the calciumtest has an oxygen transmission rate for the edge seal of less than0.005 cc/m²/day at 23° C. and 0% relative humidity, and at 38° C. and90% relative humidity. It would also have a water vapor transmissionrate of less than 0.005 g/m²/day at 38° C. and 100% relative humidity.

FIGS. 3-5 show results from calcium tests after 750 hours at 60° C. and90% relative humidity. FIG. 3 shows a successful barrier layer without aseal. The edge of the barrier layer is more than 50 mm from the calciumedge. FIG. 4 shows a successful edge seal. The edge of the barrier layeris 3 mm from the calcium edge, and no degradation is observed. FIG. 5shows an edge seal which failed. The edge of the barrier layer is 3 mmfrom the calcium edge, and severe degradation can be seen.

The number of barrier stacks is not limited. The number of barrierstacks needed depends on the substrate material used and the level ofpermeation resistance needed for the particular application. One or twobarrier stacks may provide sufficient barrier properties for someapplications. The most stringent applications may require five or morebarrier stacks.

The barrier stacks can have one or more decoupling layers and one ormore barrier layers. There could be one decoupling layer and one barrierlayer, there could be one or more decoupling layers on one side of oneor more barrier layers, there could be one or more decoupling layers onboth sides of one or more barrier layers, or there could be one or morebarrier layers on both sides of one or more decoupling layers. Theimportant feature is that the barrier stack have at least one decouplinglayer and at least one barrier layer. The barrier layers in the barrierstacks can be made of the same material or of a different material, ascan the decoupling layers. The barrier layers are typically about100-400 Å thick, and the decoupling layers are typically about1000-10,000 Å thick.

The barrier stacks can have the same or different layers, and the layerscan be in the same or different sequences.

If there is only one barrier stack and it has only one decoupling layerand one barrier layer, then the decoupling layer must be first in orderfor the barrier layer to seal it. The decoupling layer will be sealedbetween the substrate (or the upper layer of the previous barrier stack)and the barrier layer. Although a device can be made with a singlebarrier stack having one decoupling layer and one barrier layer on eachside of the environmentally sensitive device, there will typically be atleast two barrier stacks on each side, each stack having one (or more)decoupling layer and one (or more) barrier layer. In this case, thefirst layer in the stack can be either a decoupling layer or a barrierlayer, as can the last layer.

The barrier layer which seals the decoupling layer may be the firstbarrier layer in the barrier stack, as shown in barrier stack 420. Itmay also be a second (or later) barrier layer as shown in barrier stack440. Barrier layer 435 which seals the barrier stack 440 is the thirdbarrier layer in the barrier stack following two barrier layers 415which do not seal the barrier stack. Thus, the use of the terms firstdecoupling layer and first barrier layer in the claims does not refer tothe actual sequence of layers, but to layers which meet the limitations.Similarly, the terms first initial barrier stack and first additionalbarrier stack do not refer to the actual sequence of the initial andadditional barrier stacks.

The decoupling layers may be made from the same decoupling material ordifferent decoupling material. The decoupling layer can be made of anysuitable decoupling material, including, but not limited to, organicpolymers, inorganic polymers, organometallic polymers, hybridorganic/inorganic polymer systems, silicates, and combinations thereof.Organic polymers include, but are not limited to, urethanes, polyamides,polyimides, polybutylenes, isobutylene isoprene, polyolefins, epoxies,parylenes, benzocyclobutadiene, polynorbornenes, polyarylethers,polycarbonates, alkyds, polyaniline, ethylene vinyl acetate, ethyleneacrylic acid, and combinations thereof. Inorganic polymers include, butare not limited to, silicones, polyphosphazenes, polysilazanes,polycarbosilanes, polycarboranes, carborane siloxanes, polysilanes,phosphonitriles, sulfur nitride polymers, siloxanes, and combinationsthereof. Organometallic polymers include, but are not limited to,organometallic polymers of main group metals, transition metals, andlanthanide/actinide metals, or combinations thereof. Hybridorganic/inorganic polymer systems include, but are not limited to,organically modified silicates, preceramic polymers, polyimide-silicahybrids, (meth)acrylate-silica hybrids, polydimethylsiloxane-silicahybrids, ceramers, and combinations thereof.

The barrier layers may be made from the same barrier material ordifferent barrier material. The barrier layer can be made from anysuitable barrier material. The barrier material can be transparent oropaque depending on what the composite is to be used for. Suitablebarrier materials include, but are not limited to, metals, metal oxides,metal nitrides, metal carbides, metal oxynitrides, metal oxyborides, andcombinations thereof. Metals include, but are not limited to, aluminum,titanium, indium, tin, tantalum, zirconium, niobium, hafnium, yttrium,nickel, tungsten, chromium, zinc, alloys thereof, and combinationsthereof. Metal oxides include, but are not limited to, silicon oxide,aluminum oxide, titanium oxide, indium oxide, tin oxide, indium tinoxide, tantalum oxide, zirconium oxide, niobium oxide, hafnium oxide,yttrium oxide, nickel oxide, tungsten oxide, chromium oxide, zinc oxide,and combinations thereof. Metal nitrides include, but are not limitedto, aluminum nitride, silicon nitride, boron nitride, germanium nitride,chromium nitride, nickel nitride, and combinations thereof. Metalcarbides include, but are not limited to, boron carbide, tungstencarbide, silicon carbide, and combinations thereof. Metal oxynitridesinclude, but are not limited to, aluminum oxynitride, siliconoxynitride, boron oxynitride, and combinations thereof. Metal oxyboridesinclude, but are limited to, zirconium oxyboride, titanium oxyboride,and combinations thereof. Suitable barrier materials also include, butare not limited to, opaque metals, opaque ceramics, opaque polymers, andopaque cermets, and combinations thereof. Opaque cermets include, butare not limited to, zirconium nitride, titanium nitride, hafniumnitride, tantalum nitride, niobium nitride, tungsten disilicide,titanium diboride, and zirconium diboride, and combinations thereof.

The barrier layers may be deposited by any suitable process including,but not limited to, conventional vacuum processes such as sputtering,evaporation, sublimation, chemical vapor deposition (CVD), plasmaenhanced chemical vapor deposition (PECVD), electron cyclotronresonance-plasma enhanced vapor deposition (ECR-PECVD), and combinationsthereof.

The decoupling layer can be produced by a number of known processeswhich provide improved surface planarity, including both atmosphericprocesses and vacuum processes. The decoupling layer may be formed bydepositing a layer of liquid and subsequently processing the layer ofliquid into a solid film. Depositing the decoupling layer as a liquidallows the liquid to flow over the defects in the substrate or previouslayer, filling in low areas, and covering up high points, providing asurface with significantly improved planarity. When the decoupling layeris processed into a solid film, the improved surface planarity isretained. Suitable processes for depositing a layer of liquid materialand processing it into a solid film include, but are not limited to,vacuum processes and atmospheric processes. Suitable vacuum processesinclude, but are not limited to, those described in U.S. Pat. Nos.5,260,095, 5,395,644, 5,547,508, 5,691,615, 5,902,641, 5,440,446, and5,725,909, which are incorporated herein by reference. The liquidspreading apparatus described in U.S. Pat. Nos. 5,260,095, 5,395,644,and 5,547,508 can be further configured to print liquid monomer indiscrete, precisely placed regions of the receiving substrate.

Suitable atmospheric processes include, but are not limited to, spincoating, printing, ink jet printing, and/or spraying. By atmosphericprocesses, we mean processes run at pressures of about 1 atmosphere thatcan employ the ambient atmosphere. The use of atmospheric processespresents a number of difficulties including the need to cycle between avacuum environment for depositing the barrier layer and ambientconditions for the decoupling layer, and the exposure of theenvironmentally sensitive device to environmental contaminants, such asoxygen and moisture. One way to alleviate these problems is to use aspecific gas (purge gas) during the atmospheric process to controlexposure of the receiving substrate to the environmental contaminants.For example, the process could include cycling between a vacuumenvironment for barrier layer deposition and an ambient pressurenitrogen environment for the atmospheric process. Printing processes,including ink jet printing, allow the deposition of the decoupling layerin a precise area without the use of masks.

One way to make a decoupling layer involves depositing a polymerprecursor, such as a (meth)acrylate containing polymer precursor, andthen polymerizing it in situ to form the decoupling layer. As usedherein, the term polymer precursor means a material which can bepolymerized to form a polymer, including, but not limited to, monomers,oligomers, and resins. As another example of a method of making adecoupling layer, a preceramic precursor could be deposited as a liquidby spin coating and then converted to a solid layer. Full thermalconversion is possible for a film of this type directly on a glass oroxide coated substrate. Although it cannot be fully converted to aceramic at temperatures compatible with some flexible substrates,partial conversion to a cross-lined network structure would besatisfactory. Electron beam techniques could be used to crosslink and/ordensify some of these types of polymers and can be combined with thermaltechniques to overcome some of the substrate thermal limitations,provided the substrate can handle the electron beam exposure. Anotherexample of making a decoupling layer involves depositing a material,such as a polymer precursor, as a liquid at a temperature above itsmelting point and subsequently freezing it in place.

One method of making the composite of the present invention includesproviding a substrate, and depositing a barrier layer adjacent to thesubstrate at a barrier deposition station. The substrate with thebarrier layer is moved to a decoupling material deposition station. Amask is provided with an opening which limits the deposition of thedecoupling layer to an area which is smaller than, and contained within,the area covered by the barrier layer. The first layer deposited couldbe either the barrier layer or the decoupling layer, depending on thedesign of the composite.

In order to encapsulate multiple small environmentally sensitive devicescontained on a single large motherglass, the decoupling material may bedeposited through multiple openings in a single shadow mask, or throughmultiple shadow masks. This allows the motherglass to be subsequentlydiced into individual environmentally sensitive devices, each of whichis edge sealed.

For example, the mask may be in the form of a rectangle with the centerremoved (like a picture frame). The decoupling material is thendeposited through the opening in the mask. The layer of decouplingmaterial formed in this way will cover an area less than the areacovered by the layer of barrier material. This type of mask can be usedin either a batch process or a roll coating process operated in a stepand repeat mode. With these processes, all four edges of the decouplinglayer will be sealed by the barrier material when a second barrier layerwhich has an area greater than the area of the decoupling layer isdeposited over the decoupling layer.

The method can also be used in a continuous roll to roll process using amask having two sides which extend inward over the substrate. Theopening is formed between the two sides of the mask which allowscontinuous deposition of decoupling material. The mask may havetransverse connections between the two sides so long as they are not inthe deposition area for the decoupling layer. The mask is positionedlaterally and at a distance from the substrate so as to cause thedecoupling material to be deposited over an area less than that of thebarrier layer. In this arrangement, the lateral edges of the decouplinglayer are sealed by the barrier layer.

The substrate can then be moved to a barrier deposition station (eitherthe original barrier deposition station or a second one), and a secondlayer of barrier material deposited on the decoupling layer. Since thearea covered by the first barrier layer is greater than the area of thedecoupling layer, the decoupling layer is sealed between the two barrierlayers. These deposition steps can be repeated if necessary untilsufficient barrier material is deposited for the particular application.

When one of the barrier stacks includes two or more decoupling layers,the substrate can be passed by one or more decoupling materialdeposition stations one or more times before being moved to the barrierdeposition station. The decoupling layers can be made from the samedecoupling material or different decoupling material. The decouplinglayers can be deposited using the same process or using differentprocesses.

Similarly, one or more barrier stacks can include two or more barrierlayers. The barrier layers can be formed by passing the substrate(either before or after the decoupling layers have been deposited) pastone or more barrier deposition stations one or more times, building upthe number of layers desired. The layers can be made of the same ordifferent barrier material, and they can be deposited using the same ordifferent processes.

In another embodiment, the method involves providing a substrate anddepositing a layer of barrier material on the surface of the substrateat a barrier deposition station. The substrate with the barrier layer ismoved to a decoupling material deposition station where a layer ofdecoupling material is deposited over substantially the whole surface ofthe barrier layer. A solid mask is then placed over the substrate withthe barrier layer and the decoupling layer. The mask protects thecentral area of the surface, which would include the areas covered bythe active environmentally sensitive devices. A reactive plasma can beused to etch away the edges of the layer of decoupling material outsidethe mask, which results in the layer of etched decoupling materialcovering an area less than the area covered by the layer of barriermaterial. Suitable reactive plasmas include, but are not limited to, O₂,CF₄, and H₂, and combinations thereof. A layer of barrier materialcovering an area greater than that covered by the etched decouplinglayer can then be deposited, sealing the etched decoupling layer betweenthe layers of barrier material.

To ensure good coverage of the edge of the decoupling layer by thebarrier layer, techniques for masking and etching the decoupling layerto produce a feathered edge, i.e., a gradual slope instead of a sharpstep, may be employed. Several such techniques are known to those in theart, including, but not limited to, standing off the mask a shortdistance above a polymer surface to be etched.

The deposition and etching steps can be repeated until sufficientbarrier material is deposited. This method can be used in a batchprocess or in a roll coating process operated in a step and repeat mode.In these processes, all four edges of the decoupling layer may beetched. This method can also be used in continuous roll to rollprocesses. In this case, only the edges of the decoupling material inthe direction of the process are etched.

Alternatively, two masks can be used, one for the decoupling materialand one for the barrier material. This would allow encapsulation with anedge seal of device which has electrical contacts which extend outsidethe encapsulation. The electrical contacts can remain uncoated (orrequire only minimal post-encapsulation cleaning.) The electricalcontacts will typically be thin layer constructions that are sensitiveto post-encapsulation cleaning or may be difficult to expose byselective etching of the encapsulation. In addition, if a mask isapplied only for the decoupling material, a thick barrier layer couldextend over the areas between the devices and cover the contacts.Furthermore, cutting through the thick barrier layer could be difficult.

As shown in FIGS. 6 and 7, the mask 500 for the decoupling material hasa smaller opening than the mask 505 for the barrier material. Thisallows the barrier layer 510 to encapsulate the decoupling layer 515.

The masks 500, 505 can optionally have an undercut 520, 525 that keepsthe deposited decoupling material and/or barrier material fromcontacting the mask at the point where the mask contacts the substrate530. The undercut 520 for the decoupling mask 500 can be sufficient toplace the decoupling mask contact point 535 outside edge of barrierlayer 510, as shown in FIG. 7.

If a composite is made using a continuous process and the edged sealedcomposite is cut in the transverse direction, the cut edges will exposethe edges of the decoupling layers. These cut edges may requireadditional sealing if the exposure compromises barrier performance.

One method for sealing edges which are to be cut involves depositing aridge on the substrate before depositing the barrier stack. The ridgeinterferes with the deposition of the decoupling layer so that the areaof barrier material is greater than the area of decoupling material andthe decoupling layer is sealed by the barrier layer within the area ofbarrier material. The ridge should be fairly pointed, for example,triangular shaped, in order to interrupt the deposition and allow thelayers of barrier material to extend beyond the layers of decouplingmaterial. The ridge can be deposited anywhere that a cut will need to bemade, such as around individual environmentally sensitive devices. Theridge can be made of any suitable material, including, but not limitedto, photoresist and barrier materials, such as described previously.

While certain representative embodiments and details have been shown forpurposes of illustrating the invention, it will be apparent to thoseskilled in the art that various changes in the compositions and methodsdisclosed herein may be made without departing from the scope of theinvention, which is defined in the appended claims.

1. A method of making an edge-sealed, encapsulated environmentallysensitive device comprising: providing an environmentally sensitivedevice on a substrate; placing an edge-sealed barrier stack adjacent tothe environmentally sensitive device, the edge-sealed barrier stackcomprising a decoupling layer and at least two barrier layers, whereinthe decoupling layer has an area, wherein the first barrier layer has anarea, and wherein the second barrier layer has an area, the area of thefirst and second barrier layers being greater than the area of thedecoupling layer, and wherein the decoupling layer is sealed between thefirst and second barrier layers; wherein at least one barrier layer ofthe edge-sealed barrier stack is in contact with the substrate, sealingthe environmentally sensitive device between the substrate and theedge-sealed barrier stack forming an environmentally sensitive deviceseal, wherein an oxygen transmission rate through the environmentallysensitive device seal is less than 0.005 cc/m²/day at 23° C. and 0%relative humidity.
 2. The method of claim 1 wherein the edge-sealedbarrier stack is formed by: depositing a first barrier layer having anarea; depositing a decoupling layer having an area; depositing a secondbarrier layer having an area; the area of the first and second barrierlayers being greater than the area of the decoupling layer wherein thefirst decoupling layer is sealed between the first and second barrierlayers.
 3. The method of claim 2 wherein depositing the decoupling layercomprises: providing a mask with an opening; and depositing thedecoupling layer through the opening in the mask so that the area of thedecoupling layer is less than the area of the first and second barrierlayers.
 4. The method of claim 3 wherein the mask has an undercut. 5.The method of claim 2 wherein depositing the first or second barrierlayer comprises: providing a mask with an opening; and depositing thefirst or second barrier layer through the opening in the mask so thatthe area of the first or second barrier layer is greater than the areaof the decoupling layer.
 6. The method of claim 5 wherein the mask hasan undercut.
 7. The method of claim 2 wherein depositing the decouplinglayer comprises: depositing the decoupling layer having an initial areaof decoupling material which is greater than the area of the decouplinglayer; and etching the decoupling layer having the initial area toremove a portion of the decoupling material so that the decoupling layerhas the area of the decoupling layer.
 8. The method of claim 7 whereinetching the decoupling layer comprises: providing a solid mask over thedecoupling layer having the initial area of decoupling material; andetching the decoupling layer having the initial area of decouplingmaterial to remove the portion of the decoupling material outside thesolid mask so that the decoupling layer has the area of the decouplinglayer.
 9. The method of claim 7 wherein the decoupling layer is etchedso that at least one edge of the decoupling layer has a gradual slope.10. The method of claim 7 wherein the decoupling layer is etched using areactive plasma.
 11. The method of claim 10 wherein the reactive plasmais selected from O₂, CF₄, H₂, or combinations thereof.
 12. The method ofclaim 1 wherein placing the edge-sealed barrier stack adjacent to theenvironmentally sensitive device comprises laminating the edge-sealedbarrier stack adjacent to the environmentally sensitive device.
 13. Themethod of claim 12 wherein the edge-sealed barrier stack is laminatedadjacent to the environmentally sensitive device using a processselected from heating, soldering, using an adhesive, ultrasonic welding,and applying pressure.
 14. The method of claim 2 wherein the first andsecond barrier layers are depositing using a vacuum process.
 15. Themethod of claim 2 wherein the decoupling layer is deposited using aprocess selected from vacuum processes or atmospheric processes.
 16. Themethod of claim 2 wherein the decoupling layer is deposited using anatmospheric process selected from spin coating, printing, ink jetprinting, spraying, or combinations thereof.